The underworld

Welcome to the underworld.
The railroad tunnel, a concrete canvas,
Hidden from the summer heat.
Cool and and musty, you can feel the train coming,
Through the ground beneath your feet.
The painters, they look like monks,
Their hoodies pulled over their heads.
Shaking their Krylon spray cans,
With rattlesnake sounds,
Stepping over mildewed sleeping bag beds.
Someone in ragged clothes will sleep here tonight.
With a small fire and something cheap to drink.
He'll get to see the latest masterpiece.
A Mona Lisa, with a wink.